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The size and composition of abomasal worm burdens from 143 casualty and cull dairy heifers were estimated. Over 60 per cent had totals of less than 10,000, only four exceeded 100,000 and the overall mean was 16,285. Ostertagia ostertagi was almost always present and usually formed the major proportion of the total. Trichostrongylus axei was recorded in 83 heifers and was the most common species on 17 occasions. The numbers of arrested early fourth stage worms were highest in winter and declined rapidly during spring. O lyrata was only found when O ostertagi was present and always as a small percentage of the total. Similarly in the case of two of the minor species, Skrjabinagia kolchida (= Grosspiculagia podjapolskyi) was never found independently of O leptospicularis (= O crimensis). These relationships are regarded as suggestive of polymorphism.

A study of anthelmintic treatments received by 40,000 cattle during 1978 on a random sample of 240 farms in England and Wales showed that most were given against gastrointestinal nematodes for purposes of prophylaxis. Analysis of the data indicates that of an estimated pounds 15m spent on anthelmintics and their administration, most was far less effectively employed than it might have been. Errors of three kinds were common, some classes of cattle being dosed unnecessarily, animals being dosed at an unfavourable occasion or time of year, and anthelmintics being directed at parasites against which they had no action. Existing knowledge on the control of helminths is not effectively used; most dosing was done without advice from an identifiable source.